1. Field of the Invention
The present invention relates to a flexible film weir formed of a flexible film and laid across a river or the like, which is erected when air or a liquid such as water is supplied and falls flat when air or a liquid such as water is discharged.
2. Description of the Related Art
Water gates, weirs for protecting a lake and the like are generally made of steel and are large-scale installations.
Thus, one which is generally referred to as a "rubber weir" wherein a flexible film weir is erected and laid flat by supplying and discharging air or liquid such as water is often used for a river because its construction is easy. A weir of this kind can also be used as a water gate or a weir for protecting a lake.
Unlike one that is provided in the middle of the river, however, in a water gate or a weir for protecting a lake, the water levels of both sides of it may sometimes be reversed. Thus, water gates and weirs for protecting a lake need to stay erected with stability in all circumstances.
Additionally, as a water gate or a weir is opened when the water levels of both sides of it are equal, it is desirable that the flexible film weir falls completely flat when the water levels of both sides of it are equal.
However, if air is used, the film may be partially floated by the air that is trapped in the bag-like body when the weir falls flat, or some portions of the film do not come into close contact with the river bed even when the air is not trapped inside. The floating part and portions that are not in close contact with the river bed float in the water, thereby making it difficult to lay the flexible film weir completely flat.
Particularly, when the weir is provided in thoroughfares used by shipping, in some cases the portions floating in the water may come into contact with the bottom of a vessel.
In order to solve the aforementioned problems, Japanese Patent Application Laid-Open (JP-A) No. 62-45811 discloses forming irregularities on the river bed or mounting objects for forming irregularities (for example, tubes, sticks, or the like) on the river bed. However, the labor required to form irregularities or the cost of the objects for forming irregularities raises the problem of high cost.
Further, a flexible film weir of this type requires a structure to absorb the redundant length thereof as its configuration changes in accordance with the supply and discharge of the air. Thus, the concern exists that the structure may become complicated.